Pictures produced by the instant-development method and taken from a scene which has been illuminated by such multiflash units, exhibit a bright center and dark border zones. Instantly developed color pictures may additionally exhibit a color shift.
The film material used in instant-development picture-taking differs from the material conventionally used in picture-taking by its highly reduced exposure tolerance. In order to obtain an instantly developed picture of satisfactory quality, it is therefore vitally important to provide uniform scene illumination. The heretofore available multiflash units are not yet adequate in this regard, for they furnish a light distribution curve with a distinct and prominent maximum in the region of the reflector axis, and a falling off towards the side zones of the reflector due to the protective shield covering the reflector-lamp assembly, which heretofore has generally been transparent in the area immediately covering the lamp. On account of the nature of instant-picture film, it would be desirable to provide a rise of the light distribution at the lateral borders with concurrent lowering of the central maximum to the level at the border. A light distribution curve even with a dip in the center would be particularly advantageous.